Teamskip's low-carb mix from Trueprotein.com
The chocolate tastes like chocolate, it mixes w/o a blender, it's not expensive and doesn't taste like chalk. The premium flavors are the best.
If you don't order a jug and a scoop it will come in a food grade bag w/o anything else. (scoops and jugs are not expensive and you only need to order one the first time, then you just refill the jug with your next order.)